Page 41 - Principles of Catalyst Development
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STRUCTURE  OF  CATALYSTS                                          27
                                                   function:
                                                     high surface  area
                                                     porosity
                    function:                        mechanical properties
                      chemical  activity             stability
                    types:                           dual  functional
                                                      activity
                      metals                         modification  of
                      semlcond uc tor                 active  component
                       and  sulfides
                      insulator  oXides              types:
                       and  sulfides                   high  m.  p.  oxides
                                                       cloys
                                                       carbon



                                     PROMOTERS

                                    function:
                                      on  support
                                        structural
                                        activity  inhibition
                                        activity  promotion
                                      on  active  component
                                        electronic
                                        morphology
                                        poisoning
                                 Figure  2.2.  Catalyst components.




                         TABLE  2.1.  Classification of Active Components
                           Conductivity I
                             Reaction
               Class          type           Reactions             Examples

             Metals       Conductors       Hydrogenation        Fe, Ni, Pt
                          Redox            Hydrogenolysis       Pd, Cu, Ag
                                           Oxidation
             Oxides and   Semiconductors   Selective            NiO, ZnO, CuO
               sulfides   Redox              hydrogenation
                                           Hydrogenolysis       Cr20], MoS 2
                                           Oxidation
             Oxides       Insulators       Polymerization       AI 20"  Si0 2 ,  MgO
                          Carbonium ions   Isomerization        SiOr Al 2O,
                                           Cracking
                                           Dehydration          Zeolites
   36   37   38   39   40   41   42   43   44   45   46